Method of thiocarbamoylchitosan obtainment

FIELD: chemistry.

SUBSTANCE: method of obtaining thiocarbamoylchitosan (TCC) involves chitosan reaction with ammonium rhodanide solution in organic thiocarbamide solvent at 110-150°C at weight ratio of chitosan to ammonium rhodanide of 100 : 90 - 440, with further water extraction of cooled reaction mass and product drying.

EFFECT: obtainment of TCC with addition degree of 0,31-1,12.

1 tbl, 7 ex

 

The invention relates to the synthesis of thiocarbamoyl derivatives of polysaccharides, namely the method of obtaining thiocarbamoylation (tariff and qualifying characteristics). These compounds are used as components of antibacterial agents and as sorbents of heavy metals.

Known only way to obtain tariff and qualifying characteristics by reacting chitosan with a 11% solution of ammonium thiocyanate in ethanol by heating the mixture under reflux (temperature ~80°C) and stirring for 12 hours at a ratio of 100 g of chitosan 91 g of ammonium thiocyanate. After sorption of silver ions the product is used as antibacterial agents (Carbohydr. Polym. 2005, 60, 33-38; CN1712417 A).

The disadvantage of this method of obtaining tariff and qualifying characteristics is the use of alcohol solutions when heated, which requires the inverse of the refrigerator, i.e., not only heating, but also cooling unit. Chitosan in alcohol insoluble, so the reaction proceeds in a heterogeneous system under stirring - this allows to obtain tariff and qualifying characteristics with a sulfur content not higher than 0,6% (corresponds to degree of annexation - 0,035).

Because sorption properties of tariff and qualifying characteristics in relation to ions of silver (or any other heavy metal ions), and thus a unique antimicrobial properties of silver derivatives, due to the number of entered thiocarbamoyl groups (residues tibmachuni the s), the most valuable should be considered as target product - tariff and qualifying characteristics with a greater degree of connection.

The problem solved by the invention is a simplified method of obtaining tariff and qualifying characteristics and improve its quality.

The problem is solved by the interaction of chitosan with a solution of ammonium thiocyanate in the thiourea (concentration of ammonium thiocyanate 32-68%) at a ratio of 100 g of chitosan from 90 to 440 g of ammonium thiocyanate at 110-150°C for 4-6 hours, extraction of the cooled reaction mixture with water and subsequent drying of the product.

Use as an organic solvent thiourea does not require the use of a reverse refrigerator. The formation of chitosan in the proposed conditions of homogeneous gel allows you to carry out the process without stirring at 110-150°C. the process Time is reduced by 2-3 times, the degree of annexation thiocarbamoyl groups increases 9-32 times (0,31-1,12) with the same or greater value of the yield of the target product, which allows more efficient use of the equipment and increases the value of tariff and qualifying characteristics for use as a sorbent.

At temperatures below 110°C, the inhomogeneous environment that slows down the process, above 150°C is markedly reduced yield due to processes of degradation of the polymer chain. Carrying out the reaction for smaller periods of time (less than 4 hours) inefficient because the degree is of prisoedinenia low (less than 0.3), large periods of time (over 6 hours) does not lead to a further increase in the degree of connection.

The process is carried out by heating in the reactor, the product is then extracted with water to conventional Soxhlet extractions, dried in a drying Cabinet with air. The composition of the obtained tariff and qualifying characteristics characterize the content of S and N % of the data of elemental analysis, the presence of introduced thiocarbamoyl groups - IR spectroscopy using consoles diffuse reflection.

The proposed solution is illustrated by the following examples.

Example 1

A mixture of 3.3 g (0.02 mol) of chitosan, and 10.5 g (is 0.135 mol) of ammonium thiocyanate and 5 g (0,065 mol) of thiourea are heated up to 130°C, incubated 10 min before the formation of gel-like mass is then heated at the same temperature for 6 h and cooled. The resulting product is subjected to cold extraction water (to conventional Soxhlet extractions) to negative reactions to the thiocyanate ion (ferric salt). The product is dried at 50°C until constant weight, the yield of 3.8, According to the elemental analysis of sulfur content is 12,11%, which corresponds to the degree of annexation by 1.12. In the IR spectrum of the product has an absorption band 1620 cm-1characteristic relation S=C, and 1404 cm-1for S=C-N<.

Examples 2-6

The method further experiments corresponds to example 1. Reaction conditions and characteristics of the products obtained are presented in Alice 1.

Table 1.
Conditions for obtaining tariff and qualifying characteristics and features.
No.chitosan, gNH4SCN, g (%)CS(NH2)2gmass. aspect]. NH4SCN: chitosantemperature, °Ctime, h*gS %**degree accession
the placeholder16,115,2 (11)ethanol 12090:100~801210,60,035
13,310,5 (68)5300:10013061,212,111,12
24,95a 21.75 (68)10,35440:10010 51,17,870,56
35,9412,42 (32)26,1440:10013051,210,480,78
43,965,04 (68)2,4130:10013041,19,260,75
52,481,58 (68)0,7590:100130614,760,31
60,581,87 (50)1,87320:1001504113,760,45
*Output per 1 g of the loaded chitosan.
** Degree of attach (DS) was calculated by the formula DS=1/(nN/nS-1), where nN/nS- the molar ratio between the elements determined from the data of elemental analysis.

The method of obtaining thiocarbamoylation interaction of chitosan with a solution of ammonium thiocyanate in an organic solvent by heating, characterized in that the organic solvent used thiourea, the reaction is carried out at a temperature of 110-150°C and the mass ratio of chitosan:ammonium thiocyanate 100:90-440 with subsequent extraction of the cooled reaction mixture with water and drying the product.



 

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